Wednesday, 30 September 2015

Major east coast rain event as Joaquin forms in Atlantic

A poorly timed cold front produced heavy rain and snarled traffic during the Tuesday evening commute in Montreal. (ValleyWX)
 Tuesday was very warm across southern Quebec, perhaps the last really muggy day of 2015. Temperatures reached 25C (77F) in Montreal, well above the normal high of 17C (63F). A cold front plowed into the St. Lawrence Valley during the evening commute with very heavy rain. Nearly 20mm fell in less than one hour in Montreal, with 35mm as of 7am this morning. As much as 51mm fell in Kemptville, Ontario with the frontal passage. Light rain continues in Montreal this morning, but the heavy rain has settled south along the US border and into New England. The front has stalled over those regions and is acting like a conveyor transporting copious amounts of tropical moisture into the northeast. Rainfall may exceed 100mm (4 inches) from Pennsylvania and New York into southern New England and the Maritimes. Numerous flood watches and warnings are on place including heavy rain warnings for the Eastern Townships. High pressure will slowly clear out southern Quebec over the next 24 hours, but it will be much cooler along with stiff northwest winds up to 50km/h. Low temperatures in Montreal will drop to 5C (41F) with highs around 14C (56F).

The current NHC forecast track for Joaquin.
Tropical Storm Joaquin
Another major player in the flood potential shaping up along the east coast will be the future track of tropical storm Joaquin. The storm developed in the Atlantic this week and is located 240 miles east northeast of the Bahamas this morning. Joaquin has 70 mph winds but is strengthening and will likely reach hurricane status today. Joaquin is expected to drift west southwest over the next 24 hours before moving north. The storm may impact portions of the eastern US and Canada beginning as early as Sunday with torrential rain. One forecast model has the storm approaching northern New England and southern Quebec by late Monday. Another has it remaining over the Atlantic. This storm will have to be monitored very closely, especially for coastal regions from North Carolina to Nova Scotia. The National Hurricane Center forecast models have Joaquin reaching Category 2 strength with winds in excess of 100mph. With most of the area from the middle Atlantic north being saturated with the current rain event, the potential for major flooding is very real.

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